<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <style>
      body, ul, li,select {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
ul,li {list-style: none;}
.calculator {
    max-width: 300px;
    margin: 20px auto;
    border: 1px solid #eee;
    border-radius: 3px;
}
.cal-header {
    font-size: 16px;
    color: #333;
    font-weight: bold;
    height: 48px;
    line-height: 48px;
    border-bottom: 1px solid #eee;
    text-align: center;
}
.cal-main {
    font-size: 14px;
}
.cal-main .origin-value {
    padding: 15px;
    height: 40px;
    line-height: 40px;
    font-size: 20px;
    text-align: right;
    overflow: hidden;
    text-overflow:ellipsis;
    white-space: nowrap;
}
.cal-main .origin-type,
.cal-main .target-type {
    padding-left: 5px;
    width: 70px;
    font-size: 14px;
    height: 30px;
    border: 1px solid #eee;
    background-color: #fff;
    vertical-align: middle;
    margin-right: 10px;
    border-radius: 3px;
}
.cal-keyboard {
    overflow: hidden;
}
.cal-items {
    overflow: hidden;
}
.cal-items li {
    user-select: none;
    float: left;
    display: inline-block;
    width: 75px;
    height: 75px;
    text-align: center;
    line-height: 75px;
    border-top: 1px solid #eee;
    border-left: 1px solid #eee;
    box-sizing: border-box;
}
li:nth-of-type(4n+1) {
    border-left: none;
}
li[data-action=operator] {
    background: #f5923e;
    color: #fff;
}
.buttons {
    float: left;
    width: 75px;
}
.buttons .btn {
    width: 75px;
    background-color: #fff;
    border-top: 1px solid #eee;
    border-left: 1px solid #eee;
    height: 150px;
    line-height: 150px;
    text-align: center;
}
.btn-esc {
    color: #ff5a34;
}
.btn-backspace {
    position: relative;
}
    </style>
</head>
<body>
    <div class="calculator">
    <header class="cal-header">简易计算器</header>
    <main class="cal-main">
        <div class="origin-value">0</div>
        <div class="cal-keyboard">
            <ul class="cal-items">
                <li data-action="num">7</li>
                <li data-action="num">8</li>
                <li data-action="num">9</li>
                <li data-action="operator">÷</li>
                <li data-action="num">4</li>
                <li data-action="num">5</li>
                <li data-action="num">6</li>
                <li data-action="operator">x</li>
                <li data-action="num">1</li>
                <li data-action="num">2</li>
                <li data-action="num">3</li>
                <li data-action="operator">-</li>
                <li data-action="num">0</li>
                <li data-action="operator">清空</li>
                <li data-action="operator">=</li>
                <li data-action="operator">+</li>
            </ul>
        </div>
    </main>
</div>
    <script type="text/javascript">
/*
展示了一个简化版的计算器
1. 除法操作：如果被除数为0， 则结果为0
2. 结果如果为小数，最多保留小数点后两位，如 2/3 = 0.67 1/2 = 0.5
3. 阅读并根据提示补充完成函数initEvent， result 和 calculate
4. 不要手动修改html 和 css
5. 不要使用第三方插件
 */
//
var Calculator = {
    init: function () {
        var that = this;
        if (!that.isInited) {
            that.isInited = true;
            // 保存操作信息
            // total: Number, 总的结果
            // next: String, 下一个和 total 进行运算的数据
            // action: String, 操作符号
            that.data = {total: 0, next: '', action: ''}; // 表达式解析：一组哈希值保存操作信息
            that.bindEvent();
        }
    },
    bindEvent: function () { // 事件绑定：点击table对应位置，向操作栏加载数据和操作符
        var that = this;
        // 请补充代码：获取 .cal-keyboard 元素
        var keyboardEl = document.querySelector(".cal-keyboard");
        keyboardEl && keyboardEl.addEventListener('click', function (event) {
            // 请补充代码：获取当前点击的dom元素
            var target = event.target;
            // 请补充代码：获取target的 data-action 值
            var action = target.dataset.action;
            // 请补充代码：获取target的内容
            var value = target.innerText;
            if (action === 'num' || action === 'operator') {
                that.result(value, action === 'num');
            }
        });
    },
    result: function (action, isNum) { //
        var that = this;
        var data = that.data;
        if (isNum) {
            data.next = data.next === '0' ? action : (data.next + action);
            !data.action && (data.total = 0);
        } else if (action === '清空') {
            // 请补充代码：设置清空时的对应状态
            data.total = 0;
            data.next = "";
            data.action = "";
        } else if (action === '=') {
            if (data.next || data.action) {
                data.total = that.calculate(data.total, data.next, data.action);
                data.next = '';
                data.action = '';
            }
        } else if (!data.next) {
            data.action = action;
        } else if (data.action) {
            data.total = that.calculate(data.total, data.next, data.action);
            data.next = '';
            data.action = action;
        } else {
            data.total = +data.next || 0;
            data.next = '';
            data.action = action;
        }

        // 补充代码：获取 .origin-value 元素
        var valEl = document.querySelector(".origin-value");
        // print(data)
        valEl && (valEl.innerHTML = data.next || data.total || '0');
    },
    calculate: function (n1, n2, operator) { // 表达式计算
        n1 = +n1 || 0;
        n2 = +n2 || 0;
        if (operator === '÷') {
            // 请补充代码：获取除法的结果
            return n2 === 0 ? 0 : Math.floor((n1 / n2) * 100) / 100;
        } else if (operator === 'x') {
            // 请补充代码：获取乘法的结果
            return Math.floor((n1 * n2) * 100) / 100;
        } else if (operator === '+') {
            // 请补充代码：获取加法的结果
            return Math.floor((n1 + n2) * 100) / 100;
        } else if (operator === '-') {
            // 请补充代码：获取减法的结果
            return Math.floor((n1 - n2) * 100) / 100;
        }
    }
};
Calculator.init();
    </script>
</body>
</html>